Animals that magically transform under the full moon is purely the stuff of myths and legends, but the full moon does make some animals dramatically change their behavior. For the Barau's petrel, that's when they suddenly become romantic.

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This tropical bird is one of a few species that effectively reserves all its sexual impulses for the full moon. The birds return to their mating sites on Reunion Island, which is just off the coast of the island nation of Madagascar. For the mating season to be successful, it's imperative that the birds all get there at the same time, and that's where the full moon becomes so crucial. It serves as a sort of signal for all the birds, telling them it's time to meet up and make babies.

Many birds use light cues to figure out when it's time to migrate north or south. But the Barau's petrel is unusual in that it migrates east to west, which means it stays on the same tropical latitude year round. Without any clues from changing amounts of sunlight, the full moon becomes the most reliable way for the species to sync up when it's time to migrate.

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It's an ingenious solution that the species has evolved, and so the full moon has now become synonymous with sex, at least for this one species. French researchers who have studied the birds for the last two years also say the full moon affords some extra advantages. Their research shows the birds spend up to 80% of full moon nights in the air as opposed to resting on the water, which means they're doing their night flying when there is maximum visibility. This also allows them to hunt some nocturnal prey that otherwise would be too difficult to see without all that moonlight.